Temperature response of permafrost soil carbon is attenuated by mineral protection

authored by

Norman Gentsch, Birgit Wild, Robert Mikutta, Petr Čapek, Katka Diáková, Marion Schrumpf, Stephanie Turner, Cynthia Minnich, Frank Schaarschmidt, Olga Shibistova, Jörg Schnecker, Tim Urich, Antje Gittel, Hana Šantrůčková, Jiři Bárta, Nikolay Lashchinskiy, Roland Fuß, Andreas Richter, Georg Guggenberger

Abstract

Climate change in Arctic ecosystems fosters permafrost thaw and makes massive amounts of ancient soil organic carbon (OC) available to microbial breakdown. However, fractions of the organic matter (OM) may be protected from rapid decomposition by their association with minerals. Little is known about the effects of mineral-organic associations (MOA) on the microbial accessibility of OM in permafrost soils and it is not clear which factors control its temperature sensitivity. In order to investigate if and how permafrost soil OC turnover is affected by mineral controls, the heavy fraction (HF) representing mostly MOA was obtained by density fractionation from 27 permafrost soil profiles of the Siberian Arctic. In parallel laboratory incubations, the unfractionated soils (bulk) and their HF were comparatively incubated for 175 days at 5 and 15°C. The HF was equivalent to 70 ± 9% of the bulk CO₂ respiration as compared to a share of 63 ± 1% of bulk OC that was stored in the HF. Significant reduction of OC mineralization was found in all treatments with increasing OC content of the HF (HF-OC), clay-size minerals and Fe or Al oxyhydroxides. Temperature sensitivity (Q10) decreased with increasing soil depth from 2.4 to 1.4 in the bulk soil and from 2.9 to 1.5 in the HF. A concurrent increase in the metal-to-HF-OC ratios with soil depth suggests a stronger bonding of OM to minerals in the subsoil. There, the younger ¹⁴C signature in CO₂ than that of the OC indicates a preferential decomposition of the more recent OM and the existence of a MOA fraction with limited access of OM to decomposers. These results indicate strong mineral controls on the decomposability of OM after permafrost thaw and on its temperature sensitivity. Thus, we here provide evidence that OM temperature sensitivity can be attenuated by MOA in permafrost soils.

Organisation(s)

Institute of Soil Science
Department of Biostatistics
Leibniz Research Centre FZ:GEO

External Organisation(s)

University of Vienna
Austrian Polar Research Institute
Stockholm University
Martin Luther University Halle-Wittenberg
University of South Bohemia
Max Planck Institute of Biogeochemistry (MPI-BGC)
Federal Institute for Geosciences and Natural Resources (BGR)
University of Bayreuth
Russian Academy of Sciences (RAS)
University of New Hampshire
University of Greifswald
University of Bergen (UiB)
Aarhus University
Johann Heinrich von Thünen Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries

Type

Article

Journal

Global change biology

Volume

24

Pages

3401-3415

No. of pages

15

ISSN

1354-1013

Publication date

03.07.2018

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Global and Planetary Change, Environmental Chemistry, Ecology, General Environmental Science

Sustainable Development Goals

SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.1111/gcb.14316 (Access: Closed)